Ecommerce shop for digital products with multi-vendors

We need an ecommerce website where users can upload their products (audio, video or images) and sell them. The website is going to take a fee from each user. There will be 2 kinds of fees: 1) fixed fees - a user will pay one time for getting his product on the website (for a fixed period of time), something like [login to view URL] 2) percent fees - a user will not pay any fee but instead he will pay a % for every sale he makes. It will need to have a shopping cart, payment methods (paypal and moneybookers), a way for sellers to get money to their account (once a sale is made) and a way to withdraw money. Some sites with similar functions: [login to view URL] and [login to view URL] For customization purposes, i would like to use Joomla + VirtueMart. But if you have a better idea i would really love to hear it. The total budget for this is $1,800 and the payment terms are as follows: 80% after installing the final website on our server and 20% after 5 days of testing. The winner will need to sign an NDA and contract regarding this project. Has to be ready really fast, 2 weeks max, if you can get it done faster, a bonus is available. If you miss the deadline there will be penalty of 10% per day. The main graphics are already done, it won't be anything complicated, really simple light graphics. The functionality is the most important. If you need any other info, use the PM system.